Cowboys co-captain Tom Dearden and his girlfriend Millie Oliver have welcomed their first child, with their baby daughter arriving in the middle of his Rugby League World Cup campaign.

The couple announced the arrival of Dolly June Dearden on Monday, revealing she was born on October 23.

Sydney hairdresser Millie shared the happy news on social media, describing their daughter as 'the best birthday present I could have ever asked for'.

The Cowboys also celebrated their newest supporter, posting a congratulatory message to the couple.

Dearden, 25, has been juggling his first days of fatherhood with Australian representative duties, taking the field against Fiji in Brisbane just two days after Dolly's birth.

His Cowboys and Kangaroos teammate Reuben Cotter said the proud new dad had wasted little time getting involved at home.

Speaking at Townsville Airport on Monday, Cotter revealed Dearden was spending a few days with his family in Sydney before returning to the Australian squad.

Cotter told the Townsville Bulletin that Dearden was already handling nappy changes and overnight parenting duties.

The happy announcement comes after the couple's private lives became the subject of intense scrutiny earlier this year, when speculation linked Dearden with a move away from North Queensland.

Millie runs a hair salon in Bella Vista in Sydney, and reports in July suggested her ability to settle in Townsville could influence the playmaker's future.

The Cowboys repeatedly rejected suggestions their captain was looking to leave.

Dearden then addressed the rumours himself in August, firmly denying he wanted out of the club and reaffirming his commitment until the end of 2029.

He also revealed the speculation had taken a toll on his pregnant partner and family, who had been left answering questions about their personal lives.

'I'm not recommitting or anything like that, I've always been committed to the Cowboys and none of that has ever changed,' he said at the time.

The scrutiny followed a frustrating run with injuries for Dearden, who missed the entire State of Origin series after suffering a syndesmosis injury.

A subsequent injury to his opposite leg added to his disrupted season.

Now back in Australian colours, Dearden is competing with Roosters halfback Sam Walker for a starting position alongside Cameron Munster as the World Cup moves towards the knockout stages.

Coach Kevin Walters faces a decision over his preferred halves combination following Australia's win over Fiji on Sunday.